Topic 7: Equilibrium

Question 1

What is the equilibrium law?

Answer 1

It states that at a given temperature the ratio of the concentration of products to the concentration of reactants is a constant, called equilibrium constant, Kc.

Question 2

Kc&raquo_space; 1

Answer 2

at a given temperature, products are favoured over reactants

Question 3

Kc &laquo_space;1

Answer 3

very small Kc indicates that the reaction is unfavourable at this given temperature

Question 4

Change in reaction equation when the reaction is reversed

Answer 4

1/Kc

Question 5

Change in reaction equation when the coefficients are halved.

Answer 5

square root Kc

Question 6

Change in reaction equation when the coefficients are doubled

Answer 6

Kc2

Question 7

Change in reaction equation when reactions are summed

Answer 7

Kc = Kc(1) x Kc(2) x …

Question 8

What’s the Chatelier’s principle?

Answer 8

‘If a change is made to a system that is in equilibrium, the balance between the forward and reverse reactions will shift to offset this change and return the system to equilibrium.’

Question 9

What is the Haber process?

Answer 9

A process that can manufacture ammonia on a large scale.
Main applications are: fertilizers, manufacture of plastics, fibres, explosives and pharmaceuticals.

Ammonia reacts with nitric acid to form ammonium nitrate, which is used as a fertiliser.
HNO3(aq) + NH3(g) → NH4NO3(aq)

Question 10

What are the effects of pressure on reaction in the gas phase?

Answer 10

A shift in the equilibrium position towards the side of fewer moles of gas.
Kc does not change, if the temperature remains constant.

Question 11

What are the effects of temperature on reaction?

Answer 11

For the exothermic reaction, an increase in temperature will shift the equilibrium in the direction that will consume the extra energy, ie the equilibrium position will move to the left, favouring the reactants, resulting decrease in the equilibrium constant K

Question 12

What are the effects of a catalyst on reaction?

Answer 12

In a reversible reaction, the lowered activation energy has an equal effect on both the forward and reverse reactions. The position of the equilibrium will not change and there is no effect on the equilibrium constant Kc
q??ck

Question 13

What is the reaction quotient Q?

Answer 13

it helps to determine how far away the system is from achieving equilibrium.

Question 14

Q > Kc

Answer 14

The concentration of products is greater than at equilibrium and the reverse reaction is favoured until equilibrium is reached.

Question 15

Q < Kc

Answer 15

The concentration of reactants is greater than at equilibrium and the forward reaction is favoured until equilibrium is reached

Question 16

Q = Kc

Answer 16

The system is at equilibrium and the forward and reverse reactions occur at equal rates